Is it possible to easily change the tone or length of the current tone of the chime? I want to use one on the front and back doors, and be able to tell which is which. Thanks.
I have not seen any mods for what you are looking for.
I believe all the timing and tones are in the controller chips programming.
Modifications for the X10 Chime Module
http://www.laureanno.com/x10-mod2.html
That modification is for one hardware version of the chime module.
If yours is a different revision. Then it may not be possible.
I know mine don't look like the ones in the modifications.
Looking at the PC Board would give you clues.